Primary microvibration standards down to 10^-3 m s² at low frequency

The reliability of microvibration measurements is important in some applications, such as infrastructure health monitoring. Thus, it is necessary to develop a vibration standard based on ISO16063-11 for microvibrations. In this study, the low-frequency standard vibration calibration system in the National Metrology Institute of Japan was upgraded to be compatible with small input vibrations down to an amplitude of 10(-3) m s(-2). A low-noise reference vibration measurement system and a precise signal processing method were integrated to reduce the background noise contribution, which is a dominant uncertainty source in the field of microvibration calibration. The developed system could calibrate the sensitivity of a low-noise accelerometer down to 10(-3) m s(-2), between 0.1 Hz and 100 Hz. This paper reports the calibration demonstration using a servo accelerometer and the evaluated uncertainty budget. The estimated calibration uncertainty was 0.1% for a normal calibration process with an excitation of 10 m s(-2), and it was 2.1% for a microvibration calibration process with an excitation of 10(-3) m s(-2).